1. Field of the Invention
The present invention is related to a suction disc unit that can be adsorbed on a smooth surface to support a hung article, and especially to an improved design of suction disc for increasing adsorbing force and thus increasing supporting force.
2. Description of the Prior Art
A suction disc unit mainly is used to be adsorbed on a plain surface to support a hung article. Taking the U.S. Pat. Nos. 6,234,435 and 6,749,160 as examples, wherein a suction disc unit can be adsorbed on a piece of glass of a car, the suction disc unit is provided with a supporting rod and a receiving seat etc. to support a PDA or GPS etc. And as is stated in the U.S. Pat. No. 6,550,735, hanging hooks are provided on a suction disc unit, thereby a suction disc can be adsorbed on a smooth surface such as a piece of tile or glass to hang at will thereon an article of daily necessities such as a tower, a suit of clothes etc.
The above stated conventional suction disc units generally each includes thereon a pressing lid forming in its inner side a receiving space, a suction disc provided in the inner side of the pressing lid, a link provided centrally on the suction disc and a pressing rod provided in the outside of the pressing lid; the pressing lid has an eccentric protruding portion; when the suction disc abuts against the smooth surface to press down the pressing lid, the eccentric protruding portion abuts against the pressing lid, so that the pressing lid abuts against the periphery of the suction disc, and the link moves upwards to pull tight the central portion of the suction disc, hence a gap that has been in an air tight state between the suction disc and the smooth surface expands, thus the air originally in the gap presents a state of low pressure by expansion of the air, now the air pressure in the gap is much lower than that of the atmosphere to thereby induce a strong suction force.
The bearing strength of the suction disc unit is influenced by the pressure difference between the abovementioned air in the gap and the pressure of the atmosphere in the circumstance, the larger the pressure difference is, the larger the bearing strength will be; in other words, the smaller the pressure difference is, the smaller the bearing strength of the suction disc unit will be. While the ways of lowering the air pressure in the gap have two kinds; one is to remove the air in the gap, the other is to expand the gap in case the amount of air is limited (in an air tight state).
In the above stated two U.S. Pat. Nos. 6,234,435 and 6,749,160, we can see that the mode of designing of the prior arts in increasing the bearing strength of a suction disc unit mainly takes advantage of a spring abutting on a suction disc to help removing of the air in a gap.
Therefore, when the suction disc unit is in suction, a user sticks the suction disc unit to a smooth surface, by abutting of the spring on the suction disc, the air in the gap between the suction disc and the smooth surface is removed as much as it can, in order that the suction disc unit can have larger bearing strength during subsequent expanding of the gap.
The prior arts using a spring to remove air is worth being taken for reference, however, they still have the problems such as being cumbersome in assembling and having elastic fatigue, the pushing force of each of the springs is inadequate, the distance of pushing will be reduced by such elastic fatigue . . . etc.